Cooling means for electron tubes



Oct. 22, 1957 G. J. AGULE 2,810,849

COOLING MEANS FOR ELECTRON TUBES Filed Jan. 31, 1955 INVENTOR.

GEORGE J. AGULE ATTORNEYS.

United States 2,810,849 Patented Get. 22, 1957 COOLING MEANS non ELECTRON 'fl Inns George J. Agule, Stamford, Conn., assignor to Machiett Laboratories, Incorporated, Springdale, Conn a corporation of Connecticut Application January 31, 1955, Serial No. 485,612

8 Claims. (Cl. 313-45) This invention relates to cooling or heat exchange systems for use with thermionic discharge devices and has particular reference to high powered electron tubes having radiators attached to the external anodes thereof.

In the electronics industry it is desirable and common, particularly in the manufacture of high powered electron tubes, to use external anodes formed of copper and to provide means for removing the heat generated therein during operation of the tube. The most common method for accomplishing this is to attach to the anode a radiator comprising a plurality of longitudinally extending copper fins arranged radially about the anode, and to force cool air between the fins to dissipate the heat. t is generally necessary to initially braze the fins to a copper sleeve or core to form the radiator and to subsequently solder the radiator in encircling relation to the anode in a separate assembling operation.

There are, however, a number of objections to such prior art radiators. Copper has been commonly used for the material of the radiator since it can be mounted on a copper anode and has good thermal conductivity. However, it is a relatively heavy material and on some common and extensively used high power electron tubes it is a known fact that the copper radiator alone weighs in the vicinity of 200 lbs. Such heavy tubes thus are very difficult to handle, requiring the use of hoists or other mechanical equipment for handling. Such difficulty in handling also results in increased breakage, particularly of fragiie parts within the tube. In addition, packaging and shipping costs of such heavy tubes are high.

Copper also tends to oxidize when heated and consequently is believed to lose some of its heat transfer efficiency.

In prior art tubes of this type there also occur two connections which act as partial heat transfer barriers between the anodes and the fins, these connections occurring at the solder joints between the fins and sleeves and between the sleeves and anodes. Most known efficient soldering media do not possess high thermal conductivity characteristics and, therefore, the reduction in the number of such joints is desirable.

In known prior art tubes provided with radiators of this type, the fins are generally mounted longitudinally of the anode on the copper sleeve which closely encircles the anode, heat being transmitted through the sleeve to the fins. When air is forced in the usual manner onto the bottom of such a radiator, it first strikes one end of the fins and travels along and in the plane of the fins toward the glass envelope of the tube. Thus, by the time it reaches the other end of the fins, the air becomes sufficiently hot to render negligible the cooling effect of the fins at this end andralso causes the glass envelope to become undesirably heated.

A still further objection to such prior art radiators is that when soldering copper fins onto the sleeve, for subsequent mounting on an anode, the soldering operation is necessarily performed at such high temperatures that the copper becomes undesirably soft and is thus rendered structurally weak. This is undesirable since it requires greater care in handling to prevent damage to the fins.

it is, therefore, desirable to construct a radiator which will overcome the foregoing objections, preferably by use of a light-weight material having satisfactory thermal conductivity and tendency toward little or no oxidation when heated, and which remains relatively stiff and hard after conventional fabrication techniques are completed. Aluminum, magnesium, and their alloys are known to possess most of these desirable characteristics.

Aluminum in particular has been tried many times by the industry but up to the time of the conception of this invention has always been discarded for the reason that because aluminum inherently possesses expansion characteristics different from the copper anode on which the aluminum radiator is mounted, when a tube carrying an aluminum radiator has been repetitively heated and cooled, the solder connection between the aluminum and copper becomes ruptured and thus the radiator becomes ineifective.

The present invention, therefore, is directed toward the provision of a radiator formed of aluminum or similar material, which radiator may be satisfactorily permanently attached to and used with a copper anode and which is simultaneously designed to eliminate the problem of efficient cooling at only one end as is the case with known prior art radiators of the aforementioned type.

Accordingly, it is a primary object of this invention to provide an improved radiator for an electron discharge devi e, which radiator is comprised of fins formed of a light-weight material located in relatively close engagernent with the anode and wherein the radiator has expansion characteristics generally similar to the known expansion characteristics of the anode whereby the relatively close engagement between the anode and the radiator will be retained during operation of the electron discharge device and consequent repetitive heating and cooling of the anode.

Another object is to provide a radiator of the above character for an electron discharge device wherein the radiator comprises a plurality of aluminum fins and copper spacers which are disposed in alternate arrangement and positioned in close encircling relation with the anode of the electron discharge device.

Another object is to provide a radiator of the above character wherein the fins and spacers are connected directly to the anode of the discharge device, with no intervening sleeve or core, whereby the heat from the anode is distributed relatively uniformly and efficiently directly to the fins.

Another object is the provision of a composite radiator of the above character wherein the fins and spacers are formed of materials having dififerent coefiicients of expansion, and the relative thicknesses thereof are controlled so as to provide the radiator with expansion characteristics such that the stresses on the connection between the radiator and the anode are reduced to a negligible value during operation of the device.

A further object is the provision of an electron tube with a radiator which comprises a plurality of alternately arranged aluminum fins and copper spacers whichare shaped for mounting in close encircling relation to the anode of the tube, and which may be easily, quickly, simply and inexpensively soldered in place thereon in a single operation.

A further object is the provision of an electron tube having a radiator of the above character thereon wherein the overall weight and size of the tube are considerably reduced, and wherein the radiator has little or no tendency to oxidize.

Other objects and advantages of this invention will become apparent from the following description taken in connection with the accompanying drawing, wherein is shown a front elevational view partly in vertical section of an electron tube embodying a preferred form of the invention.

The tube shown in the drawing is an external anode type of power tube wherein a metallic anode It) is secured to one end of a dielectric envelope 11 as by a seal 12. Positioned within the anodeis a cathode filament structure 13, the strands thereof being attached by suitable clips 14 t'o one end of a' group of filament-supporting posts 15, '16, and 17. Posts 15 and 16 are connected at their opposed ends to respective terminals which extend through the end of the envelope 11, one of these terminals only being shown and designated by numeral 18, the other terminal lying in the plane of and behind terminal 18. Post 17"terminates short ofthe connections to the filament terminals and thus functions to aid in properly supporting the filament strands. i

The filament structure 13 lies within a grid structure which comprises a cylindrical arrangement of spaced wires 19 having one end extending'into a tubular shield 20 and secured to the inner surface thereof. The shield 20 has a radial flange 21 connected by bolts 22 or other suitable means to the adjacent ends of a pair of grid terminals 23 which'extend through the envelope l1 and are spaced diametrically apart substantially 90 from the filamen terminals.

The opposed ends of the grid wires 19 extend into a metal cup 24 and are secured to the inner surface thereof, and a supporting wire '25 is wound helically around wires 19.

In operation of a tube of this type it is apparent that electrons will flow from the filament structure 13 through and under control of the grid structure 19 to the anode 'The anode 10 is preferably formed of copper and, upon operation of the tube, is heated and expanded a predetermined amount.

Mounted upon and secured directly to the outer surface of the anode 10 is a radiator 26 which comprises a plurality of radially extending fins 27and spacers 28 arranged in alternate order, the fins 27 being preferably annular in shape and secured directly to the anode 10 throughout their. entire inner peripheries'to provide good heat conductivity from the anode 10. The spacers 28 are also preferably annular in shape and secured through- V out their inner peripheries directly to the anode surface.

However, the outside diameter of the spacers 28 is relatively small. Thus, a considerable area of both surfaces of each fin is. exposed to the air, providing excellent means of dissipating heat from the anode 10.

To increase the exposed surface area, the fins 27 are formed relatively thin and thus allow for use of fins in gfileater numbers than would be the case if the fins were t 'ck.

The fins 27 may be made of any suitable light-weight metal such as aluminum, magnesium or their alloys. The spacers 28 may be copper, steel or other material having a diflferent coefficient of expansion than the fins 27. Aluminum is preferable for the fins since it is light weight, stiff, durable, readily workable, and has good thermal conductivity. Copper, however, is preferred for the spacers 28 because ithas a coefficient of expansion similar to the anode 10. j

In accordance with this'in'vention, the fins 27 are made of aluminum or other material having expansion char-' acteristics different than the material of the spacers 28 and it is important, therefore, to control the relative thick nesses of the fins and spacers. For example, if the aluminum fins 27 are made to a thickness of approximately .025 in, and spacers 28 of. copper are approximately .050 in. thick, and theknown expansion in units per unit length per degree centigrade betweenZO and 100. degrees centigrade 'of commercially available 52 aluminum is 23.5 l0 units and copper 165x10 units, then the resultant axial expansion of the combined fin-spacer radiator unit will be approximately 18 .8 1O- units. In addition, since theanode 10 runs about 10% higher in temperature than the adjacent portion of the radiator and consequently expandsabout 18.15 X10 units, this is sufliciently close to the radiators expansion of l8.8 10- units to be satisfactory. Where the relative expansions of the anode and radiator are quite different, separation therebetween is likely to occur during use of the tube with resultant decrease of cooling efficiency of the anode. It is to be understood, however, that if other materials are used for the fins or spacers, the relative thicknesses thereof should be likewise controlled so that the resultant expansion of the radiator will be suflicie'ntly close to the expansion of the anode as to introduce little stress in the connection between the radiator and anode and maintain the close physical relationship therebetween.

It has been found that the heavy prior art tube referred to hereinbefore can be provided with an aluminum radiator of the presently described type, instead of a copper radiator constructed as taught by the prior art, which will not only be smaller in overall size but will be reduced in weight from approximately 200 lbs. to about 30 lbs.

A preferred means of providing a tube with a radiator of this type is to provide the aluminum fins 27 with an initial nickel plating and to initially coat the spacers 28 with cadmium or other selected soldering material. Then the fins 27 and spacers 28 are stacked on a mandrel in alternate order to orient and axially align them. A spring-actuated fixture is preferably applied to compress the group of fins and spacers, after which the mandrel is withdrawn. Then if the fins and spacers are to be connected and the radiator is to be attached to an anode in a single simultaneous operation, the anode is inserted within the structure in place of the mandrel. Then heat is applied of an amount suflicient'to melt the cadmium or other soldering material which will flow onto the anode and fins, and upon cooling and hardening, will simultaneously seal the spacers and fins together and to the anode. Additional soldering materialmay. be added as desired in any known manner.

It is to be understood, of course, that the radiators can be made for subsequent attachment to anodes if desired by assembling without presence of the anode.

It is apparent from the foregoing that an improved radiator for electron discharge devices has been provided in accordance with the objects of this invention. It is to be understood, however, that a radiator of the character described may be used with other types of electron discharge devices having external heated elements other than the type shown and described. The presently described radiator is not only light in weight, small in overall'siz'e, and relatively rugged and durable, but also is efiicient in coolingdue to having only a single efiective aluminum when the unitis cooled from soldering temperature. Since the temperature of the unit is not thereafter raised during operation to the melting point of the solder, subsequent heating merely results in partial relief of this compression. a

While the novel features of the invention have been shown and described, and are pointed out in the annexed claims, it is to be understood that various changes may be made by those skilled in the art without departing from the spirit of the invention. Therefore, all matter shown or described is to be interpreted as illustrative and not in a limiting sense. a

I claim:

1. A radiator for an electron discharge device having an anode of known expansion characteristics adapted to be heated during operation of the electron device, the radiator comprising a plurali'y of fins and spacers mounted in alternate order for close encircling engagement with the anode, the fins and spacers being respectively of materials having difierent expansion characteristics and being of different thicknesses in accordance with the different expansion characteristics such that the radiator as a unit has expansion characteristics generally similar to the expansion characteristics of the anode whereby upon operation of the electron discharge device and consequent heating of the anode the close relation between the anode and encircling parts of the radiator is retained.

2. A radiator for an electron discharge device having an anode of known expansion characteristics adapted to be heated during operation of the electron device, the radiator comprising a plurality of fins and spacers mounted in alternate order for close encircling engagement with the anode, the fins being relatively thin and of a material having a known coefiicient of expansion, and the spacers having a known coeflicient of expansion less than the material of the fins and also being formed to controlled thicknesses greater than the thicknesses of the fins, the radiator as a unit having expansion characteristics generally similar to the expansion characteristics of the anode when heated whereby upon operation of the electron discharge device and consequent heating of the anode the close encircling relation between the radiator and anode is retained.

3. A radiator for an electron discharge device having an anode of known expans1on characteristics adapted to be heated during operation of the electron device, the radiator comprising a plurality of fins and spacers mounted in alternate order for close encircling engagement with said anode, the fins being thin sheets of light weight metal having a relatively high coefficient of expansion, the spacers being of material heavier than the material of the fins and having a lesser coefiicient of expansion, the radiator as a unit having expansion characteristics generally similar to the expansion characteristics of the anode when heated whereby upon operation of the electron discharge device and consequent heating of the anode the close encircling relation between the radiator and anode is retained.

4. A radiator for an electron discharge device having a copper anode of known expansion characteristics adapted to be heated during operation of the electron discharge device, the radiator embodying a plurality of relatively thin aluminum fins and annular copper spacers mounted in alternate order for close encircling relation with the anode, the spacers being of smaller diameter and greater thickness than the respective diameter and thickness of the fins, the respective thicknesses of the fins and spacers being controlled according to the difference in thermal expansion characteristics thereof whereby the radiator as a unit has expansion characteristics generally similar to the expansion characteristics of the anode when heated whereby upon operation of the electron discharge device and consequent heating of the anode the close encircling relation therewith is retained.

5. A high power electron tube comprising an envelope, a cathode within the envelope, an anode secured to the envelope and having a portion extending externally thereof, ahd a radiator mounted on said anode comprising a plurality of fins and spacers mounted in alternate order and in close encircling engagement with the anode,

the fins and spacers being respectively of materials having difierent expansion characteristics and being of different thicknesses in accordance with the difierent expansion characteristics such that the radiator as a unit has expansion characteristics generally similar to the expansion characteristics of the anode whereby upon operation of the electron discharge device and consequent heating of the anode the close relation between the anode and encircling parts of the radiator is retained.

6. A high power electron tube comprising an envelope, a cathode within the envelope, an anode secured to the envelope and having a portion extending externally thereof, and a radiator mounted on said anode comprising a plurality of fins and spacers mounted in alternate order and in close encircling engagement with the anode, the fins being relatively thin and of a material having a known coeflicient of expansion and the spacers being of a material having a coefficient of expansion less than the material of the fins and also being formed to controlled thicknesses greater than the thicknesses of the fins, the radiator as a unit having expansion characteristics generally similar to the expansion characteristics of the anode when heated whereby upon operation of the electron discharge device and consequent heating of the anode the close encircling relation between the radiator and anode is retained.

7. A high power electron tube comprising an envelope, a cathode within the envelope, an anode secured to the envelope and having a portion extending externally thereof, and a radiator mounted on said anode comprising a plurality of fins and spacers mounted in alternate order and in close encircling engagement with said anode, the fins being thin sheets of light weight metal having a relatively high coeificient of expansion, the spacers being of material heavier than the material of the fins and having a lesser coefiicient of expansion, the radiator as a unit having expansion characteristics generally similar to the expansion characteristics of the anode when heated whereby upon operation of the electron discharge device and consequent heating of the anode the close encircling relation between the radiator and anode is retained.

8. A high power electron tube comprising an envelope, a cathode within the envelope, an anode secured to the envelope and having a portion extending externally thereof, and a radiator mounted on said anode comprising a plurality of relatively thin aluminum fins and annular copper spacers mounted in alternate order and in close encircling relation with the anode, the spacers being of smaller diameter and greater thickness than the respective diameter and thickness of the fins, the respective thicknesses of the fins and spacers being controlled according to the difierence in thermal expansion characteristics thereof whereby the radiator as a unit has expansion characteristics generally similar to the expansion characteristics of the anode when heated whereby upon operation of the electron discharge device and consequent heating of the anode the close encircling relation therewith is retained.

References Cited in the file of this patent UNITED STATES PATENTS 2,289,984 Mouromtsefi et a1. July 14, 1942 2,399,752 McCullough May 7, 1946 2,444,080 Williams June 29, 1948 2,458,693 Drieschman et a1. Jan. 11, 1949 2,477,122 Garner July 26, 1949 

